Gabriela Lucano-Ramírez

Variaciones espaciales y temporales de la abundancia de peces juveniles en la laguna costera Barra de Navidad, Jalisco, México: Efectos del huracán

espanolSe evaluo la variacion espacio-temporal de la ictiofauna juvenil en la laguna costera Barra de Navidad, Jalisco, Mexico. Las muestras se tomaron en dos periodos: Marzo 2011 a febrero 2012 en el sitio 1 y octubre 2012 a noviembre 2013 en los sitios 1 y 2. Durante el primer periodo de muestreo, ocurrio el paso del huracan Jova (octubre 2011) y este fenomeno, introdujo un nuevo factor en el analisis. Las capturas se realizaron utilizando un chinchorro playero. Se registraron la salinidad, temperatura y granulometria del sedimento. Un total de 36.897 individuos de 61 especies fueron colectados y su longitud total fue medida. El 90% de las especies y el 96% de los individuos aparecieron como juveniles. Cuatro taxones (Anchoa spp., Eucinostomus currani, Diapterus peruvianus y Mugil spp.) conformaron mas del 80% de las capturas en numero. Se encontraron diferencias significativas en la composicion de la ictiofauna entre periodos de muestreo y entre estaciones del ano para el sitio 1, mientras que se encontraron diferencias significativas entre sitios y entre epocas del ano durante el segundo periodo. Se encontro una diferencia significativa en la composicion de las asociaciones de peces antes y despues del paso del huracan Jova en el sitio 1. Se concluye que los fuertes cambios de salinidad son la causa mas probable de los cambios en las asociaciones de peces a lo largo del ano, mientras que las diferencias en la granulometria del sedimento y el porcentaje de materia organica explicaron las diferencias entre sitios. EnglishSeasonal and spatial variations of nearshore juvenile fish assemblages were assessed inside the coastal lagoon of Barra de Navidad, Jalisco, Mexico. Sampling was carried out during 2 different periods: March 2011 to February 2012 in site 1 and October 2012 to November 2013 in sites 1 and 2. During the first sampling period, the hurricane Jova (October 2011) hits the study area and introduced an unpredicted environmental impact. Samples of fish assemblages were taken using a beach purse seine. Water salinity, temperature and sediment granulometry were measured. A total of 36,897 individuals of 61 species were collected and their total lengths were measured. 90% of the species and 96% of the individuals were classified as juvenile. Four taxa (Anchoa spp., Eucinostomus currani, Diapterus peruvianus and Mugil spp.) made more than 80 percent of catches in number. Significant differences were found in fish assemblage composition between sampling periods and between seasons for site 1, while significant differences were found between sites and between seasons for the second sampling period. A significant difference was found in the composition of fish assemblages before and after the hurricane Jova at site 1 during the first sampling period. Strong seasonal changes in salinity are most probably the cause of changes found in fish assemblages along the year, while differences in sediment granulometry and organic matter percentages could explain differences between sampling sites.

Fishes as indicators of untreated sewage contamination in a Mexican coastal lagoon

Lagoons are important nursery habitats for fishes but are often sites of intense human activity including wastewater discharges. The goal of this research was to compare stable nitrogen (δ15N) and carbon (δ13C) isotopes, total mercury (THg) and other metal levels in four selected fish species among sites with different levels of untreated sewage discharge inside Barra de Navidad coastal lagoon in the Mexican Pacific. Three species from sites heavily impacted by sewage showed higher δ15N and δ13C compared to those from non-impacted sites. In addition, the highest concentrations of THg were present in fish of two species (Sciades guatemalensis and Diapterus brevirostris) collected at the two most impacted sites, and exceeded the 0.2μg/g ww threshold believed to be protective of adult and juvenile fish. No individuals of Achirus mazatlanus and Mugil curema exceeded this threshold, and liver somatic index and condition did not distinguish high from low impacted sites for all species. In general, the metal levels differed among species but not sites, and were lower than what has been measured in fishes elsewhere. The study also provides the first information on several fish species for coastal areas of Mexico, suggests that THg and isotopes can distinguish sewage-impacted sites, and can serve as a baseline for future studies.